JP3042168B2 - Single crystal manufacturing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing a single crystal, and more particularly to an apparatus for producing a single crystal suitable for producing a semiconductor using the Bridgman method.

[0002]

2. Description of the Related Art As a method of manufacturing a semiconductor single crystal used as a substrate for various semiconductor elements such as a field effect transistor, a Schottky barrier diode, an integrated circuit (IC), a crystal growth method from a melt is a mainstay. In the crystal growth method from the melt, it is required to precisely control the shape of the crystal growth surface (solid-liquid interface) from the start to the end of the crystal growth. In the pulling method, which is one of the methods for growing crystals from the melt, the crystal growth surface is controlled by controlling the rotation speed of the crucible, the rotation speed of the crystal, and the pulling speed. However, such a pulling method has a large temperature gradient and cannot reduce the dislocation density.

[0003] As a method for producing a low-dislocation-density crystal having a constant diameter under a low temperature gradient, a boat method requiring no diameter control is suitable. There are a horizontal type and a vertical type in the boat method, but a vertical boat growth method in which a melt is solidified in a crucible as it is to obtain a single crystal is effective for increasing the diameter. The vertical boat growth method includes a vertical Bridgman method (VB method) and a temperature gradient solidification method (VGF method). The former VB method is a method of growing a single crystal by mechanically changing the relative position of the main heater and the crucible, while the latter VGF method is a method of heating the heater without changing the positional relationship between the heater and the crucible. This is a method of growing a single crystal by changing the temperature distribution. This vertical Bridgman method or VGF method is suitable for manufacturing large-diameter circular wafers. However, this boat method is different from the pulling method in which the growing crystal is pulled from the melt while rotating and solidified.
Because of the feature of the static state change, it is impossible to control the crystal growth surface by controlling the rotation speed or the like, and the crystal growth surface is controlled by devising a hot zone structure.

FIG. 3 shows an example (WA Gaul).
t et. al. J. C. G 74 (1986) 491
506). In FIG. 3, a raw material melt 8 is prepared in the crucible 3 and an inorganic compound semiconductor (hereinafter, referred to as “III-V group”) composed of Group IIIb and Vb elements of the Periodic Table upward from the seed crystal 6 accommodated in the bottom of the crucible. Compound semiconductor)
In a crystal growth method (for example, a vertical Bridgman method, etc.) for solidifying the single crystal (crystal 7), a groove 14 was formed in the susceptor 4 holding the crucible 3, and an attempt was made to control the thermal environment and heat flow near the susceptor 4. It is an example. FIG. 4 (a),
Arrows in (b) indicate the heat flow in the initial and late stages of crystal growth, respectively. Susceptor 4 provided with groove 14
Can control the dissipation of heat from the crystal in the early stage of crystal growth.

That is, by providing a groove serving as a heat insulating portion in the susceptor, the heat flow in the horizontal direction among the heat flows passing through the susceptor can be suppressed, and the heat flow in the horizontal direction of the crystal can be controlled.
However, in the method of controlling the heat flow with such a susceptor having a groove, the effect is naturally limited to the vicinity of the susceptor, and the effect is significantly reduced at a place away from the susceptor. As shown in FIG. 4 (b),
In the latter stage of the crystal growth, there is almost no effect of the susceptor provided with the groove 14 as compared with FIG. 4A, and there is a large heat flow in the lateral direction. There is a big difference.

By the way, in crystal growth from a melt,
The shape of the crystal growth surface largely depends on the heat flow in the vicinity of the crystal growth surface. In order to control the shape of the crystal growth surface, it is necessary to control the heat flow throughout the entire crystal growth.
In the crystal growth by the above method, it is difficult to control the heat flow in the latter stage of the crystal growth, and a method of controlling the heat flow over the entire crystal growth is strongly desired for improving the quality of the crystal. In order to solve such a problem, Japanese Patent Laying-Open No. 3-80181 discloses that an auxiliary heating element is used.
It was a wasteful method considering energy efficiency.

[0007]

In crystal growth from a melt, it is essential to precisely control the crystal growth surface over the entire crystal growth in order to obtain a uniform and high-quality crystal. It is necessary to precisely control the heat flow through the crystal, especially the heat flow near the crystal growth surface (solid-liquid interface).

[0008]

The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, provided a portion near the solid-liquid interface of the susceptor wall with a reduced heat insulation rate for taking in the radiant heat of the heater. As a result, they have found that such a problem can be solved, and have reached the present invention. That is, an object of the present invention is to provide a method capable of controlling the heat flow during crystal growth without newly using energy, and such an object is to provide a single crystal at one end of a vertically arranged crucible. A seed crystal is placed, a crucible is filled with a raw material, and the raw material is heated, melted, solidified to grow the seed crystal, and a single crystal manufacturing apparatus for obtaining a single crystal is provided with a susceptor wall near a solid-liquid interface. It is easily attained by a single crystal manufacturing apparatus characterized in that the heat insulation rate is reduced.

Hereinafter, the present invention will be described in more detail. FIG. 1 is a diagram showing one embodiment of the present invention. The basic structure of the device may be a conventional one. Briefly describing the entire apparatus, the single crystal manufacturing apparatus is housed in an airtight container 1 and a heat insulating material 2 is provided immediately inside the container. A heating element 3 is disposed inside the heating element 3 so as to surround the crucible 5 held by the susceptor 4. The crucible 5 contains a seed crystal 6, a single crystal 7 grown from the seed crystal 6, a raw material melt 8, and a sealant 9. The solid-liquid interface is 10. The susceptor base 4 is connected to a support rod 11, and the solid-liquid interface 10 is maintained at a fixed position by moving the support rod 11 up and down. Susceptor wall 13
Has a structure that does not move even if the crucible 5 fixed to the heat insulating material 2 or the airtight container 1 moves. As such an apparatus, a conventionally used single crystal manufacturing apparatus may be used as it is.

The feature of the present invention resides in that a portion 12 of the susceptor wall 13 is provided near the solid-liquid interface 10 in the vicinity of the solid-liquid interface 10 and has a reduced heat insulation rate. This portion is hereinafter referred to as a reduced thickness portion 12 for convenience. By providing this reduced thickness portion 12,
Solidification from the melt near the inner wall of the crucible is less likely to occur, and the single crystal is less likely to be disturbed. The area of the reduced thickness portion 12 and the thickness to be reduced are determined in consideration of the diameter of the growing single crystal, the amount of latent heat depending on the material, the ease with which the heat flows, the output of the heater, the thermal conductivity of the heat insulating material, and the like. Those skilled in the art may arbitrarily set the values.
The shape of the thinned portion 12 may be simply reduced as a whole, but, for example, the thickness becomes thinnest at a portion corresponding to the solid-liquid interface, and thereafter the thickness is continuously changed. It is more preferable to carry out the contrivance. Further, the heat insulation rate may be reduced by changing the type of the heat insulating material, and further, for example, a small hole may be provided in the heat insulating material. A method of opening the window is also conceivable. The most preferred of these is a method of opening a window in a heat insulating material that can be easily implemented.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below by taking a GaAs single crystal as an example. GaAs in BN crucible of φ3 inch
It was charged using 1500 g of s polycrystal and 400 g of B ₂ O ₃ as raw materials. The seed crystal used <100> orientation. The atmosphere gas is nitrogen and 7 atm. A hole having a height of 25 mm and a width of 24 mm was formed near the solid-liquid of the susceptor wall. The crucible rotation speed was 3 rpm.

A single crystal was formed over a length of 8 cm.
The obtained single crystal is cut at (100) perpendicular to the pulling axis.
At 390 ° C. for 10 minutes. This result
The results are shown in FIG. No window drilling for comparison
The result performed using the conventional susceptor wall is shown.
In the conventional method, the average EPD is 11000 / cm ^TwoAnd high, especially
It was increasing in the periphery. On the other hand, in the method according to the present invention, the average
EPD6700 / cm^TwoAnd low around the crystal
D did not increase significantly. In addition, lineage
Not at all.

[0013]

According to the present invention, since the solidification of the semiconductor melt from the crucible wall is less likely to occur, single crystal growth is smoothly performed. Further, the EPD can be made uniform. Further, polycrystallization can be prevented, and improvement in productivity can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one example of a single crystal manufacturing apparatus of the present invention.

FIG. 2 is a diagram comparing density of crystal defects of a single crystal manufactured by a single crystal manufacturing apparatus of the present invention and a single crystal manufactured by a conventional single crystal manufacturing apparatus by using EPD.

FIG. 3 is an explanatory view showing an example of a single crystal manufacturing apparatus conventionally used for improving the shape of a crystal growth surface.

FIG. 4 is an explanatory diagram showing a heat flow during single crystal growth in a conventional single crystal manufacturing apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 airtight container 2 heat insulating material 3 heating element 4 susceptor 5 crucible 6 seed crystal 7 single crystal 8 raw material melt 9 sealing material 10 solid-liquid interface 11 support rod 12 reduced thickness portion 13 susceptor wall 14 groove

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-80180 (JP, A) JP-A-58-2290 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C30B 1/00-35/00

Claims (1)

(57) [Claims] Claims 1. A crucible vertically arranged has a single crystal at one end, and a seed crystal, which is a single crystal, is placed inside the crucible, and the raw material is heated, melted, and solidified to grow the seed crystal. A single crystal manufacturing apparatus for obtaining a single crystal, wherein a heat insulation rate of a susceptor wall near a solid-liquid interface is reduced.